1. Field of the Invention
The present invention relates to a hybridoma which produces an anti-thymosin .alpha.1 monoclonal antibody, an antibody produced thereby, and a method for measurement of thymosin .alpha.1 by an immunological sandwich method using said antibody.
2. Discussion of the Background
Thymosin .alpha.1 is one of the thymus factors produced by thymus tissue. It is a polypeptide having a differentiation-inducing activity on T cells and plays an important role in maintenance of immunological functions. A polypeptide has been found in cattle that has the same amino acid sequence as that of human thymosin .alpha.1. Thymosin .alpha.1 consists of 28 amino acid residues and the first Ser [1] at the N-terminus is acetylated.
As a method for measuring thymosin .alpha.1, radioimmunoassays (RIA) which employ antisera have already been established (U.S. Pat. No. 4,264,571; U.S. Pat, No. 4,339,427; International Journal of Immunopharmacology 14, 1267-1278, 1992; Journal of Immunological Methods 110, 261-265, 1988; Molecular Immunology 23, 701-707, 1986; Journal of Immunological Methods 89, 9-17, 1986; and Journal of Immunological Methods 80, 45-53, 1985). Such immunoassays, which utilize a monoclonal antibody or a polyclonal antibody that recognize thymosin .alpha.1, have all been either competitive RIA or competitive enzyme immunoassays (EIA), using a labeled antigen. In these immunoassays, thymosin .alpha.1 which is labeled with a radioactive or non-radioactive labeling material does not exhibit exactly the same antigenecity to the anti-thymosin .alpha.1 antibody as the thymosin .alpha.1 present in a living body. In competitive immunoassays, not only thymosin .alpha.1 but a fragment of thymosin .alpha.1 or a peptide having a similar amino acid sequence also possibly participate so that high specificity for thymosin .alpha.1 has not been obtained. Also, the known immunoassays have not had satisfactory sensitivity.
The anti-thymosin .alpha.1 monoclonal antibodies and the anti-thymosin .alpha.1 polyclonal antibodies used in the above methods recognize only one part of thymosin .alpha.1. However, if one could obtain an antibody which specifically recognizes the N-terminus of thymosin .alpha.1, particularly the acetylated Ser [1] which is physiologically important, and another antibody which specifically recognizes the C-terminus of thymosin .alpha.1 then a sandwich immunoassay method would be available. The sandwich method is advantageous from the viewpoint of sensitivity and specificity as compared with the competition method.